Unitary liquid polysulfide polymer composition

ABSTRACT

A unitary polysulfide polymer composition protected from moisture and capable of being stored in a condition stable in a single container without undergoing curing and capable of being cured on contact with moisture in the atmosphere, said composition comprising (a) 100 parts by weight of a liquid polysulfide polymer, (b) a curing agent capable of being activated in the presence of an acid, and (c) 0.5 to 10 parts by weight of an organosilicon compound having at least one carbon atom and at least one RCOO- group, wherein R is hydrogen or a lower alkyl group, bonded to the silicon atom.

United States Patent [191' Nakanishi et al. 1 Jan. 30, 1973 [541 UNITARYLIQUID POLYSULFIDE 3,123,495 3/1964 Carpenter et a1 ..1 17/72 POLYMERCOMPOSITION 3,476,826 11/1969 Millen ..260/824 3 317 461 5/1967Plueddemann ....260/46.5 [75] Inventors: Osamu Nakanlshl, lbaraki-shl, 217 l I OSaka u; "mo Tamika, KaSatSu Shi 3,2 5,0 12/ 965 Seegman eta..260/79.1 both of Japan Primary Examiner-Donald E. Czaja [73] Assignee:Sekisui Kagaku Kogyo Kabushiki Assistant Examiner-Melvyn 1. MarquisKaisha, Osaka, Japan v Artorneywenderoth, Lind & Ponack [2?] filled:Dec. 14, 1970 i 1 ABSTRACT 2 l. N 98,203 1 pp 0 A unitary polysulfldepolymer composition protected from moisture and capable of being storedin a condi- 117/124 117/124 tion stable in a single container withoutundergoing 260/338 R,260/33.8 SB, 260/37 curing and capable of beingcured on contact with 65 G, 260/79.l,260/824 moisture in the atmosphere,said composition com- R prising (a) 100 parts by weight of a liquidpolysulfide [51] int. Cl. ..C08g 23/00 polymer a curing agent capable ofbemg activated [58] Field of Search .....260/46.5 E, 46.5 G, 79, 79.1,in presence of an acid and (C) 05 to par-ts by 260/824 R weight of anorganosilicon compound having at least one carbon atom and at least oneRCOO- group, [56] References Cited wherein R is hydrogen or a loweralkyl group, bonded UNITED STATES PATENTS to the silicsm atom- 3,586,6606/1971 Sakata et al. ..260/79 7 Claims, N0 Drawings UNIT ARY LIQUIDPOLYSULFIDE POLYMER COMPOSITION This invention relates to unitary liquidpolysulfide polymer compositions for use as sealants, adhesives and thelike.

Liquid polysulfide polymers having terminal mercapto groups (-SH) intheir molecule are cured at room temperature when mixed with a curingagent such as lead peroxide, and become rubbery elastomers havingexcellent resistance to weathering, oil, ozone or water, thus finding awide range of applications as adhesives, sealants, and the like.

It is necessary to mix the liquid polysulfide polymers and the curingagent such as lead peroxide just prior to use since the premixing ofthese with each other will result in curing of the polymers. Thisrequires troublesome labor, and a part of the polymer remaining unusedcannot be re-used because of curing. This is of course not economical.

With a view to removing these defects, attempts have been made toprovide a unitary composition comprising a liquid polysulfide polymerand a suitable curing agent in a container, which will be cured whenused as an adhesive, sealant, and the like. For example. U.S. Pat. No.3,225,017 discloses a unitary liquid polysulfide composition comprisinga liquid polysulfide polymer, a curing agent such as zinc peroxide to beactivated by the presence of moisture, and a deliquescent agent such assodium hydroxide. These unitary polysulfide polymer compositions havedefects such as poor storage stability and slow rate of curing, and havenot come into widespread use.

It is already known that metal peroxides generally accelerate the curingof activated liquid polysulfide polymers in an alkaline atmosphere, andthat certain acidic substances, such as stearic acid and oleic acid,retard the curing of liquid polysulfide polymers. Hence, prior to theinvention, no worker hit upon an idea of accelerating the curing of thepolysulfide polymer composition by an acidic substance.

An object of the present invention is to remove the aforementioneddefects of the polysulfide polymer compositions, and to provide unitaryliquid polysulfide polymer compositions having good storage stabilityand fast rate of curing.

The objects and advantages of the invention will become more apparentfrom the following description.

It has now been found that peroxides of alkali metals, alkaline earthmetals and other metals, such as zinc peroxide, cadmium peroxide,calcium peroxide or manganese dioxide as curing agents are inactive in aneutral condition, but surprisingly, are activated by a lower organicfatty acid such as acetic acid or propionic acid to cure the liquidpolysulfide polymers; and that the use of a specific organosiliconcompound, which releases a lower organic fatty acid on reaction withwater and self-condenses to a high-molecularweight compound, leads to amarked acceleration of curing the polysulfide polymer.

According to the invention, there is provided a unitary polysulfidecomposition comprising a liquid polysulfide polymer, a curing agent tobe activated in the presence of an acid, and an organosilicon compoundin which at least one carbon atom and at least one RCOO- group, whereinR is hydrogen or a lower alkyl group, are attached to the silicon atom.

The liquid polysulfide polymers that can be used conveniently in thepresent invention are the so-called polyalkylene polysulfide polymersexpressed by the general formula HSRSS-RSS-RSH the number of RSS unitsand the structures of the invention has RCOO- group bonded to thesilicon respective organic groups R. The organic group R is a saturatedaliphatic group, i.e. a divalent group consisting mainly of carbon atomsand hydrogen atoms. The group however may contain an oxygen atom orsulfur atom besides these. In this instance, the oxygen atom may bepresent as CO-C E or -OH group, and the sulfur atoms as E CS-C E orSl-l. Also usable as the liquid polysulfide polymers in the inventionare those having more than two chained sulfur atoms per unit polysulfidelinkage, and also SSH terminal groups.

Especially preferred liquid polysulfide polymers are those having amolecular weight of about 1,000 to 8,000, a viscosity of 10 to 2,000poises, and a degree of cross linkages of about 20 percent or less. Thepreferred examples include Thiokol LP-2 and Thiokol LP-32 (tradenames)produced by Thiokol Corporation, U. S. A.

The curing agent used in the invention has the property of curing theliquid polysulfide polymer upon being activated in the presence of anacid, especially a lower fatty acid such as acetic acid, propionic acidor formic acid. Such curing agent includes, for example, peroxides ofalkali metals, alkaline earth metals and other metals, specifically zincperoxide, cadmium peroxide, barium peroxide, magnesium peroxide, sodiumperoxide, calcium peroxide, or manganese dioxide. Of these, zincperoxide is especially preferred by reason of fast rate of curing andgood storage stability. Preferably, the amount of the curing agent is 5to 20 parts by weight per parts byweight of the liquid polysulfidepolymer.

The organosilicon compounds used in the invention are silane derivativesin which at least one carbon atom and at least one RCOO- group arebonded to the silicon atom. That at least one carbon atom is bonded tothe silicon atom means that the organosilicon compound has at least onecarbon atom directly bonded to the silicon atom. For instance, thisincludes a case wherein one to three alkyl groups such as methyl orethyl are bonded to the silicon atom.

In the group RCOO, R is hydrogen or a lower alkyl group, preferablyhaving one to five carbon atoms. Since the organosilicon compound usedin the present atom, it is hydrolyzed by reaction with water to releasea lower fatty acid, and the RCOO group is replaced by the HO group. Thegroups bonded to the silicon atoms have reactivity, and are condensed toeach other by dehydration reaction.

Thus, the organosilicon compound used in the invention releases a lowerfatty acid on reaction with water, and is condensed by the dehydrationreaction between HO-groups resulting from the hydrolysis. When theorganosilicon compound has 2 or more RCOO groups bonded to the siliconatoms, it releases a lower fatty acid as a result of reaction withwater, and is polycondensed to a high-molecular-weight substance. If, onthe other hand, the organosilicon compound used in .the invention hasone RCOO group, it releases a lower fatty acid as a result of reactionwith water, and two molecules of the organosilicon compound arecondensed by the dehydration reaction of the resulting HO groups, toform a dimer. When the organosilicon compound has an organic group, suchas an alkoxy group, for instance methoxy or ethoxy, having an oxygenatom directly bonded to the silicon atoms, in addition to one RCOO-group, the resulting HO-- groups react with the organic group having anoxygen directly bonded to the silicon atoms to form a condensate havingmore than 2 molecules.

As described above, the organosilicon compound used in the presentinvention releases a lower fatty acid on reaction with water, and isconverted to a polycondensate having a longer chain. This contributesgreatly to the curing of the unitary polysulfide polymer compositionofthe invention and the shortening of the curing time. An organosiliconcompound which will be converted to a high-molecular-weightpolycondensate having a long chain upon reaction with water has atendency of curing the unitary liquid polysulfide polymer composition ofthe invention faster than that which will be converted to a dimer.Hence, in comparison with those organo-silicon compounds having one RCOOgroup bonded to the silicon atom but being free from an organic grouphaving an oxygen atom bonded to the silicon atoms, organosiliconcompounds having a plurality of RCOO groups bonded to the silicon atomsor. organosilicon compounds having one RCOO- group bonded to the siliconatom and an organic group, such as -an alkoxy group, having an oxygenatom bonded to the silicon atom are preferred.

The organosilicon compounds that are used in the invention have at leastone carbon atom bonded to the silicon atoms, such as at least one alkylgroup, such as methyl or ethyl, bonded to the silicon atom. The presenceof a carbon atom bonded to the silicon atom in a high-molecular-weightsubstance which results from thereaction of the organosilicon compoundwith water to release a lower fatty acid and the subsequentself-polycondensation, serves to impart proper flexibility, suppleness,compatibility, etc. to rubbery elastomers formed by the curing of theliquid polysulfide'polymer compositions. Hence, the polycondensate ofthe organo-silicon compound used in the invention does not in any waydamage the characteristics of rubber elastomers resulting from thecuring of liquid polysulfide polymer compositions.

' The preferred examples of the organosilicon compounds that may be usedin the invention include methyl-diacetoxy-chloro-silane,dimethyl-diacetoxysilane, ethyl-triacetoxy-silane,methyl-triacetoxysilane, vinyl-triacetoxy-silane,isopropyl-triacetoxysilane, triisoamyloxy-acetoxy-silane, andmethylvinyldiacetoxy-silane. Of these, methyl-diacetoxy-chlorosilane,dimethyl-diacetoxy-silane, ethyl-triacetoxysilane andvinyl-triacetoxy-silane are liquid at room temperature, and can beeasily admixed with the liquid polysulfide polymer.Methyl-triacetoxy-silane, ethyltriacetoxy-silane andvinyl-triacetoxy-silane are especially effective on account of theirfast rate of curing the polymer. It is preferred in the presentinvention that the amount of the organosilicon compound should be 0.5 to10 parts by weight per parts by weight of the liquid polysulfidepolymer.

The production of the unitary liquid polysulfide polymer composition ofthe present invention can be performed by mixing in a dry conditiontheliquid polysulfide polymer, the curing agent to be activated in thepresence of an acid, and the organosilicon compound. The composition soobtained is not cured because of the absence of an acid. In theproduction of the unitary liquid polysulfide polymer composition of thepresent invention, the materials may be added in any order, and anymixing means can be used such as the use of a stirrer. It is necessaryhowever that the materials should be mixed in a dry condition in orderto maintain the composition anhydrous.

If desired, plasticizers such as dibutyl .phthalate, chlorinatedparaffins, or diphenyl pentachloride and fillers or pigments such ascalcium carbonate, carbon black, clay or titanium oxide may be added tothe unitary liquid polysulfide polymer composition. polysulfide polymerThe unitary liquid polysulfide composition so obtained is stored in adry condition in a suitable closed container such as a tube. In thiscondition, the composition can be maintained liquid for long periods oftime.

When the unitary liquid polysulfide polymer composition of the inventionis desired to be used as a sealant or adhesive, it is taken out of thecontainer, applied to the desired portions, and then allowed to stand inan atmosphere containing moisture, for instance in the air. The liquidpolysulfide composition of the invention then absorbs moisture, and iscured to a rubbery elastomer within a short time.

The unitary polysulfide polymer composition of the invention can becured for a muchshorter period of time than the conventionalunitaryliquid polysulfide polymer composition, and gives a rubberyelastomer having physical properties comparable to those of a rubberyelastomer of the conventional liquid polysulfide polymer. Moreover, thecomposition of the present invention has superior stability duringstorage. The unitary liquid polysulfide composition of the presentinvention has an outstanding technical significance in that its markedeffects, especially fast rate of curing, are the removal of the greatestdefect of the conventional unitary polysulfide polymer composition.

The reason for this curing of the unitary polysulfide composition of theinvention in a short period of time is not clear, but may roughly beexplained as follows:

The organosilicon compound of the invention'contained in the unitarypolysulfide polymer composition reacts with water in the air, and alower fatty acid'is released. The lower fatty acid so release activatesthe curingagent contained in the composition, whereby the curing of theliquid polysulfide polymer begins. On the other hand, in theorgano-silicon compound, H0- groups resulting from the hydrolysis reactwith each other, and by condensation, the length of the chain of theorganosilicon compound becomes longer, and the molecular weightincreases. Simultaneously, water is released. The released water againinduces the hydrolysis of unreacted organosilicon compound to release afresh lower fatty acid, and the lower fatty acid so released activatesthe curing agent. It is assumed that a water-induced reaction forutilizing moisture absorbed into the composition for the activation ofthe curing agent and a reaction of converting the organosilicon compoundto a high-molecular-weight compound proceed successively in the unitaryliquid polysulfide polymer composition. These reactions appear to be thereason for the shortening of the curing time.

In short, the unitary polysulfide polymer composition of the presentinvention comprising a liquid polysulfide polymer, a curing agent to beactivated in the presence of an acid and an organosilicon compoundhaving at least one carbon atom and at least one RCOO- group, Rv beinghydrogen or a lower alkyl group, bonded directly to the silicon atomshas much faster rate of ouring than the conventional unitary polysulfidepolymer composition. Furthermore, it gives a rubbery elastomer havingexcellent resistances to oil, whether or ozone comparable to a rubberyelastomer of the conventional liquid polysulfide polymer composition.Also, the composition of the invention has good storage stability.

The following Examples will illustrate the present invention.

EXAMPLE 1 Liquid LP-polymer 200 g (Thiokol LIP-32, tradename) Zincperoxide g The above ingredients were well mixed with a roll, and theresulting mixture was dried in vacuo for complete dehydration. In a drycondition, 4 g of methyl-triacetoxysilane was added to the mixture toform a composition. The resulting composition was charged into acartridge for a sealing gun, and stored at 20 C. and RH of 60 percent.

After a lapse of 6 months, the composition contained in the cartridgewas extruded onto a glass plate. No change was observed as compared withthe composition before storage. The composition on the glass plate losttackiness on the surface in minutes, nd was cured in 2 hours to a toughrubbery elastomer.

Separately, the mixture before adding methyltriacetoxy-silane wasallowed to stand in the atmospheric air for 6 month, but was not cured.

EXAMPLE 2 The procedure of Example 1 was repeated except that 5 g ofmethyl-diacetoxy-chlorosilane was used insted of 4 g ofmethyl-triacetoxy-silane. A part of the resulting composition wasallowed to stand on a glass plate. in 50 minutes, it lost tackiness onthe surface, and in 4 hours, was cured to a rubbery elastomer.

On the other hand, the composition was charged into a cartridge for asealing gun, and stored for 6 months at 20 C. and RH of 60 percent. Nochange was observed during the storage. When it was extruded onto aglass plate, it lost tackiness on the surface in about 50 minutes, andin 4 hours, was cured to a rubbery elastomer.

EXAMPLE 3 The procedure of Example 1 was repeated except that 6 g ofdimethyl-diacetoxy-silane was used instead of 4 g ofmethyl-triacetoxy-silane. The same tests as in Example 1 were performedas to the curing time and storage stability of the resultingcomposition. The results were the same as those obtained in Example 2.

EXAMPLE 4 Liquid polysulfide polymer 200 g (Thiokol LP-32, tradename)Cadmium peroxide 20 g Carbon black 30 g Calcium carbonate 10 g Titaniumoxide 10 g Diphenyl pentachloride 50 g The above ingredients were wellmixed with three rolls. The resulting mixture was dried in vacuo forcomplete dehydration. In a dry condition, 5 g of methyl-triacetoxysilanewas added to the mixture to form a composition. The resultingcomposition was charged into a cartridge for a sealing gun, and storedat 20 C. and RH of 60 percent. There was no change observed in thecomposition after a lapse of six months. When the composition was castin a sheet form onto a glass plate, it lost tackiness on the surface in40 minutes, and in 5 hours, was cured to a rubbery elastomer sheet.

COMPARATIVE EXAMPLE 1 Liquid polysulfide polymer 200 g (Thiokol LP-32,tradename) Carbon black 30 g Calcium carbonate l0 g Titanium oxide 10 gDiphenyl pentachloride 50 g TABLE 1 Hardness 200 Tensile Elont Shore-A)Modulus Modulus strength gation (Kg/cm) (Kg/cm) (Kg/cm) Ex. 4 52 8.5l8.6 28.3 510 Comp. Ex. 1 53 9.2 18.3 30.4 490 The results show thatthere is not significant difference in physical properties between therubbery elastomer obtained in Example 4 and that obtained in ComparativeExample 1.

EXAMPLE 5 Liquid polysulfide polymer 200 g (Thiokol LP-32, tradename)Calcium peroxide 20 g Titanium oxide 10 g Carbon Black 10 g Diphenylpentachloride 50 g The above ingredients were well mixed by means ofthree rolls, and the resulting mixture was dried in vacuo for completedehydration. In a dry condition, 4 g of methyl-triacetoxy-silane wasadded to the mixture to form a composition. The composition was chargedinto a certridge for a sealing gun, and stored at C. and RH of 60percent. There was no change in the composition after a lapse of 6months. When the composition was poured onto a glass plate and allowedto stand at room temperature, it lost tackiness on the surface inminutes,'and in about 3 hours, was cured completely to a rubberyelastomer. The physical properties of the composition obtained werefound to be similar to those of the rubbery elastomer obtained in thepresent Example. There was no significant difference in propertiesbetween the composition of this Example and the rubber elastomerobtained by using lead peroxide as the curing agent.

EXAMPLE 6 Liquid polysulfide polymer 200 g (Thiokol ILP-32, tradename)Manganese dioxide 20 g Calcium carbonate 30 g Carbon black 20 g s Diphenyl pentachloride .60 percent. The composition on the glass plate losttackiness on the surface in 40 minutes, and in 5 hours, was cured to arubbery elastomer.

On the other hand, the composition stored in the cartridge did notundergo any change during storage. After the end of the 6 monthsstorage, the composition was taken out onto a glass plate. It was curedafter a lapse of the same time as given above.

EXAMPLE 7 The procedure of Example 1 was repeated except that 200 g ofliquid polysulfide polymer (Thiokol LP-2, tradename) was used instead of200 g of the liquid polysulfidepolymer (Thiokol LP-32) to form a unitaryliquid polysulfide polymer composition. When the resulting compositionwas placed on a glass plate, it lost tackiness on the surface in 30minutes, and in 4 hours, was cured to arubbery elastomer.'0n the otherhand, when the composition was charged in a cartridge for a sealing gunand stored at 20 C. and RH of 60 percent, it did not undergo any changeduring storage for 6 months.

COMPARATIVE EXAMPLE 2 u uid 0| sulfide 1 me! 200 (T hiok l L P-32, treiiame) 8 line peroxide 20 g Carbon black 30 g The aboveingredients'were well mixed with a roll, and the resulting mixture wascompletely dehydrated by dryi n in vacuo. In a dry condition, I g ofsodium hydroxi e was added to the mixture to form a unitary polysulfidecomposition. Apart of the resulting composition was taken out on a glassplate, and allowed to stand at room temperature. The remainder wascharged into a cartridge for a sealing gun, and stored at 20 C. and RHof'60 percent. The composition on the glass plate lost tackiness on thesurface in 24 hours, and it took nearly one month until it wascompletely cured.

On the other hand, a rise in viscosity was observed in the compositionstored in the cartridge at a time about 3 months after initiation ofstorage. Thus, the composition was found to be poor in storagestability.

EXAMPLE 8 The procedure of Example I was repeated except that 6 g ofvinyl-triacetoxy-silane wasused instead of 4 g of themethyl-triacetoxy-silane. The resulting composition could be stored for6 months in a cartridge for a sealing gun with good stability. When thecomposition was taken out from the cartridge, it lost surface tackinessin 30 minutes, and was completely cured in 2 hours.

What we claim is:

1. -A unitaly polysulfide polymer composition protected from moistureand capable of being stored stably in a single container withoutundergoing curing and capable of being cured on contact with moisture inthe atmosphere, said composition comprising a. parts by weight of aliquid polysulfide polyme having terminal mercapto groups,

5 to 20 parts by weight of a curing agent for the polymer selected fromthe group consisting of zinc peroxide, cadmium peroxide, calciumperoxide, barium peroxide, magnesium peroxide, sodium peroxide andmanganese dioxide, which curing agent is capable of being activated inthe presence of an acid, and I v c. 0.5 to 10 parts by weight of anorganosilicon compound selected from the group consisting ofmethyl-triacetoxy-silane, ethyl-triacetoxy-silane,vinyl-triacetoxy-silane and isopropyl-triacetoxysilane.

2. The composition of claim 1, wherein said curing agent is zincperoxide, an said organosilicon compound is methyl-triacetoxy silane.

3. The composition of claim 1, wherein said curing agent is zincperoxide, and said organosilicon compound is ethyl-triacetoxy-silane.

4. The composition of claim 1, wherein said organosilicon compound ismethyl-triacetoxy-silane.

5. The composition of claim 1, wherein said organosilicon compound isethyl-triacetoxy-silane.

6. The composition of claim 1, wherein said organosilicon compound isvinyl-triacetoxy-silane.

7. The composition of claim 1, wherein said curing agent is zincperoxide, and said organosilicon compound is .vinyl-triacetoxy-silane.

a a a a

1. A unitary polysulfide polymer composition protected from moisture and capable of being stored stably in a single container without undergoing curing and capable of being cured on contact with moisture in the atmosphere, said composition comprising a. 100 parts by weight of a liquid polysulfide polymer having terminal mercapto groups, b. 5 to 20 parts by weight of a curing agent for the polymer selected from the group consisting of zinc peroxide, cadmium peroxide, calcium peroxide, barium peroxide, magnesium peroxide, sodium peroxide and manganese dioxide, which curing agent is capable of being activated in the presence of an acid, and c. 0.5 to 10 parts by weight of an organosilicon compound selected from the group consisting of methyl-triacetoxy-silane, ethyl-triacetoxy-silane, vinyl-triacetoxy-silane and isopropyl-triacetoxy-silane.
 2. The composition of claim 1, wherein said curing agent is zinc peroxide, an said organosilicon compound is methyl-triacetoxy-silane.
 3. The composition of claim 1, wherein said curing agent is zinc peroxide, and said organosilicon compound is ethyl-triacetoxy-silane.
 4. The composition of claim 1, wherein said organosilicon compound is methyl-triacetoxy-silane.
 5. The composition of claim 1, wherein said organosilicon compound is ethyl-triacetoxy-silane.
 6. The composition of claim 1, wherein said organosilicon compound is vinyl-triacetoxy-silane. 